Three.js embedded in iframe grows endlessly in iOS 8/9

If a file containing Three.js is embedded in a web page using an iframe

<iframe id=viewer src=document-with-threejs.html></iframe>

then the iframe grows endlessly in size when the page is viewed in Mobile Safari. This behavior has not been corrected in iOS 9 released today. This question and answer are posted to make the information easily accessible to web searches.